Central lateral line pathways are being studied by axonal degeneration and radioautographic methods in the clearnose skate, Raja eglanteria. Emphasis is being given to ascending projections beyond midbrain levels where lateral line fibers are known to terminate within a tegmental center named the lateral mesencephalic nucleus. Electrolytic lesions will be made in the lateral mesencephalic nucleus and, following postoperative survival times of 14-28 days, the brains will be fixed by perfusion and frozen sections processed by the Fink-Heimer method to depict degenerating axons and terminals. Complementary experiments will be done by injecting tritiated proline within this nucleus. Seven to 14 days postoperatively the brains will be fixed by perfusion, embedded in paraffin, the sections coated with nuclear tract emulsion, exposed 30-35 days and developed to show the distribution of silver grains representing terminations of third-order lateral line axons.